The invention relates to a circuit for converting an AC voltage into a variable voltage at a lower frequency which comprises a switch controlled so that at each period of the AC voltage it is conducting for a period which depends on the desired output voltage, a feedback loop being provided to bring the output voltage under the control of an instruction or reference signal.
Such a conversion circuit, called switched-mode circuit or chopped power supply, only consumes just the energy required for supplying a load using the output voltage. This is why it can lend itself to numerous applications.
Such a circuit has been described in the copending U.S. patent application No. 58,978 the circuit of this application forms an auxiliary power supply for a television receiver, the AC voltage being a voltage at the horizontal scan frequency and the output voltage a DC voltage.
In copending U.S. patent application No. 52,982 there is described another circuit of this type in which the output voltage is used for supplying the vertical deflector coil of a television receiver, the AC input voltage also being a voltage at the horizontal scan frequency.
The invention covers the same field of application but is however not limited thereto. It relates, generally, to voltage power supplies, for example for motors or for forming audio-frequency amplifiers or, in television, for forming a circuit for correcting the east-west cushion distortion.
The invention arises from the realization that in the circuits of the earlier above-mentioned patent applications the response time of the control means to a disturbance could be too long for certain applications. In fact, the lower limit of the response time is determined by the filtering means forming part of the conversion circuit for the measuring signal of the control means is the output voltage of the circuit which, of course, appears downstream of these filtering means whereas the feedback loop acts on the control electrode of the switch which is upstream of the filtering means.